Regardless of the type of blockchain network used, there is always the possibility of making transactions on it. No matter what type of transaction it is, once it is made it gets recorded and its authenticity must be verified by the blockchain network. This is done by computers within the blockchain that confirm that the details of the transaction are correct. After successful validation, a transaction is added to a blockchain block.
Imagine for example you’re working in a dairy and your job is to fill and cap bottles of milk. Whenever a bottle is filled up, you need to cap it and put it in the box with the other filled up bottles.
Similarly, a block has a defined capacity too. Whenever it fills up, it gets closed and chained to the previous block. In this way, every entry and all information is permanently saved to the block and stored. Consequently, we can build a transparent database and do not have to worry about any unwanted data changes since that would be impossible without leaving a trace (see below for further explanation about possible inconsistency within blocks and possible changes within a chain).
When a new block is added to the chain it gets a timestamp, a unique self-hash, and a unique hash of the previous block. Timestamps are responsible for chaining blocks together. As blocks are set in a chronological order on the timeline of a blockchain life, timestamps become a specific and immutable connection between blocks. Hash, in simple words, is just a mathematical translation of the content inside a block saved in the form of a string of numbers and letters.