In one sentence
A requirement that must be satisfied before a lender is obligated to fund, listed in the loan documents.
The longer version
Conditions precedent are the gates to funding: everything from executed documents to title, insurance, and opinions that must be in place before money moves. The loan agreement's list of them is effectively the closing checklist.
Reading the conditions precedent against the actual request list at kickoff is how closers make sure the checklist matches what the documents require.
Keep reading