A slot (just like an epoch) is simply a unit of time on Solana.

> A slot can then either contain a block or not (skipped slot).
> A slot refers to the period of time in which a slot leader produces ledger entries.
> The period of time for which each leader ingests transactions and produces a block.  

There's the concept of a `leader` in Solana. A `leader` for a particular period is the only validator that is allowed to produce a block.

Solana has a system that changes the leader frequently. The window of opportunity a leader has to produce a block before that privilege is re-assigned to a different validator is called a `slot`.