What is the difference between a lock convoy and lock/thread contention?

From wikipedia on lock convoy:

A lock convoy occurs when multiple threads of equal priority contend repeatedly for the same lock. Unlike deadlock and livelock situations, the threads in a lock convoy do progress; however, each time a thread attempts to acquire the lock and fails, it relinquishes the remainder of its scheduling quantum and forces a context switch. The overhead of repeated context switches and underutilization of scheduling quanta degrade overall performance.

From wikipedia on lock/thread contention contention:

lock contention: this occurs whenever one process or thread attempts to acquire a lock held by another process or thread. The more fine-grained the available locks, the less likely one process/thread will request a lock held by the other. (For example, locking a row rather than the entire table, or locking a cell rather than the entire row.);

Could somebody please elaborate a bit further on both of those things? To me it seems like they are essentially the same, or if they are not, then surely lock contention causes a lock convoy. Is that the case or are they separate and independent concepts? Also, I don’t understand the sentence "it relinquishes the remainder of its scheduling quantum and forces a context switch".