It's a data structure used to keep a set of transactions (It can have 5 10 15 transactions together, that's how we write it in block, how many in blocks? it depends)
A block is a data structure used to store groups of transactions. Each block contains a set number of transactions, which could be 5, 15 or more, depending on the specific blockchain protocol and the size of the transaction.
Blocks are the building blocks of blockchain, each of these contain transaction data, a timestamp, and a unique identifier. They’re linked in a chain, making a secure and immutable ledger.
The number of transactions vary based on the rules and the transaction sizes. Each block will be capped by a size limit to ensure the network remains effective and that blocks are processed in a reasonable timeframe