When you import a drawing into Revit LT, you are importing all the elements, such as blocks and external references (xrefs) from the drawing. They are all contained inside an element called an import symbol.
You can explode (disassemble) the import symbol into its next highest level elements: nested import symbols. This is a partial explode. A partial explode of an import symbol yields more import symbols, which, in turn, can be exploded into either elements or other import symbols. This is analogous to exploding in AutoCAD with nested xrefs and blocks. For example, you explode an xref into other xrefs and blocks. Those xrefs and blocks can, in turn, be exploded into more blocks and xrefs.
You can also explode the import symbol immediately into Revit text, curves, lines, and filled regions. This is a full explode.
Exploding Sketchup geometry
Because of the way Sketchup files are imported into Revit LT, they behave differently when exploded. The model will have to be exploded twice to effect a visible change.
To explode imported geometry
To explode 3D form geometry in the Family Editor
You can explode imported solid (not polymesh) geometry in the Family Editor environment.
You can adjust their position with the shape handles on planar faces. Use the free form elements to cut and join geometry.
Resulting partial explode import symbols can be exploded again by selecting them and clicking Partial Explode. You can continue to do this until all import symbols are converted to Revit elements.