Accompanying Blender 2.8’s snap to object system is snap during transform. When engaged this allows selections, e.g. meshes, keyframe markers etc., to move or transform by fixed increments based on distance or degree. As it can be toggled using a shortcut key, key/mouse combination or activated clicking an interface button, it can be used or be useful in slightly different ways depending on the context.
Design note: snap to object, snap during transform and other forms of object or grid snapping are all interrelated, some being available at the same time as others depending on the editing context and/or task being performed.
Enable/Disable Transform Snap
To activate Snap during transform so the feature is always active whilst working, click the Snap during transform button with the magnet icon centre-top of the 3D View. Alternatively press Shift + Tab. This enables snap, keeping it ON until the button is clicked again to turn it OFF (or Shift + Tab is pressed again).
Design note: when enabled all transform actions i.e. move (translate), rotate and scale, snap to increments and/or degrees regardless as to this being done by ‘widget’ or ‘freely’ – if the Move, Rotate or Scale widgets buttons are clicked (toolbar options), using the respective 3D widget orientation indicators and axes, snap is based on the active axis/axes (direction or rotation), whereas in ‘free transform’ pressing the shortcut keys G, R and S, or click-dragging the widget centre, will snap in all directions or rotations.
Where the 3D Widget is clicked will change how the object being moved, rotated or scaled behaves in relation to snapping, either locked to the active (click selected) axis/axes or moving freely in all directions/rotations.
As alternative to snap during transform being active all the time, it’s either ON of OFF using the above, it’s possible to control snap behaviour using a keyboard short and mouse combination, making the feature and its use more situationally flexible, active when needed, off when not. To do this, make a selection, press and hold the Ctrl key down then left-click drag an orientation handle/axis/axes on the 3D widget – Ctrl + left-click drag.
Design note: when using the Ctrl + left-click quick access shortcut, the Snap during transform button is OFF/shown as being inactive , the shortcut essentially bypasses the need for the button to be constantly clicked/ON.
For more situational control over snapping use the shortcut Ctrl + left-click drag by fixed increments  (show upper-left of the 3D View as distance or radius values) using the 3D widget  or freely – when used the Snap during transform button is inactive .
Once snap is enabled/active, object or selection behaviour is defined by; 1) Guides, 2) Units and 3) camera zoom. In practice this works as follows; in Scene Properties  the Units system is set to Metric with a Unit Scale of 1.000000, e.g. Unit Scale: 1.000000 , making each major grid division 1 metre (1m x 1m x 1m along each X/Y/Z axis). In the 3D View these Units settings are reflected by the grid and the way its divided, each major division being 1 meter in correspondence to Unit Scale.
Design note: using the default settings the grid displays 1:1, i.e. one major grid unit per one measurement unit. Click here for more on Units and measurement, here for more on Guides (grid settings).
By default the system is set to Metric units  (adjusted in Scene Properties ) and for each unit to be 1 metre, further subdivided in 10 sub-units, properties that define snap behaviour by determine how the 3D Views grid is divided.
Scale and Subdivisions
With a base unit set the grid can then be modified in Viewport Overlays under Guides using Scale and Subdivisions, that together, control the granularity of the grid relative to the parent unit (1m), with Scale set to 1.000 (Scale: 1.000) for example, each major grid unit equals 1m, which is further divided by 10 in Subdivisions (Subdivisions: 10) for smaller or minor increments, when objects are subsequently moved they will snap to 1m or 10cm depending on the Scenes/object focus/zoom.
Design note: for more on Viewport Overlays click here.
Guides, found in Viewport Overlays , determine the grids appearance in the 3D View, Scale and Subdivisions defining snap behaviour when objects move, larger values equate to larger snap increments/divisions.
Camera zoom and snap
Regardless of Unit Scale, grid Scale and Subdivisions, depending on the Scenes zoom level, i.e. how close to or far away the Scene camera is to grid center (0,0,0), snap behaviour will change to suit, the closer the camera is to centre the finer snap increments become, essentially being ‘zoomed-in’ to the smaller units of subdivision, the further away the larger. In this way manipulating objects and selections in relation to snap can be context sensitive to the camera.
Design note: camera zoom related snapping works in all views (View » Viewpoint » [orientation]) and perspectives (View » Perspective/Orthographic) but is more noticeable in Orthographic views, Front (NumPad 1), Right (NumPad 3), Top (NumPad 7) etc., where the grid fills the entire workspace.
Scene zoom, how far or close the camera is to a selection or grid centre, affects snap behaviour, the further away the more likely Blender is to use major grid units until they behave as the next set of subdivisions – 10 become 1.
Snap behaviour is also governed by the type or mode of snapping, i.e. what is being snapped to. By default this is Increments, however, others options are available; Vertex, Edge, Face and Volume. To select and activate, upper-centre of the 3D View, click the menu arrow (‘v’) to the right of Snap during transform  and choose an option . When objects are subsequently moved their behaviour will be determined by the Snapping option set, i.e. objects will snap to the highlighted vertex, edge, face or volume.
Design note: using an element-based snap option, the cursor changes to a circle when active, itself snapping to the nearest item based on the setting used, shown below for example snapped to a vertex.
To change the behaviour of snap so it latches on to different elements of an object or the Scene, set the Snapping mode  to Vertex, Edge, Face or Volume (click the ‘v’ to the right of Snap during transform ).