Immutability means a record becomes hard to edit or delete once it's added to the chain. People often say "can never be changed," but technically it really depends on network power, consensus rules, and chain security. On the big public blockchains, editing an old record is extremely hard and extremely costly.
Why it's hard
Changing a block's data changes its hash, which then no longer matches the blocks that follow it.
What's the benefit
It builds more trust into audit trails, certificates, transaction history, and ownership records.
What to watch out for
A transaction sent by mistake usually can't be reversed the way customer support might reset something for you.
Real-world example
Once a certificate record is put on-chain, quietly editing it later becomes very difficult.
You should see
Immutability keeps record integrity strong, but it also means mistakes aren't easily forgiven.