What are the encumbrances and the entanglements that believers are to watch out for?

The encumbrance is the "excess weight" (ogkos)—anything, inward or outward, that slows us down, as a runner in training would lay aside the weights he carries. The entanglement is the sin "which so easily entangles us"—the particular sin that ensnares us, the one we so easily get tangled up in. Notice that we are not told to lay aside what entangles someone else; every believer has his own enemies, and our responsibility is to know ourselves, recognize what hinders us, and set it aside through confession and spiritual growth so it does not keep us from finishing.