Anonymity vs Privacy in Bitcoin.
Very simply coins in Bitcoin are a immutable publicly accessible unencrypted chain of digital signatures showing amongst other things
INPUTS - showing the old digital signature/s used to spend this coin
OUTPUTS / UTXOs - showing the new digital signature/s required to spend this coin
These digital signatures require keypairs whose ownership can then be linked to a identity or person(s).
This link is not needed for Bitcoin to technically work i.e a user could be private forever on Bitcoin. With minimal / zero key pair reuse, hiding of public keys and growth of transaction volume on the network this privacy is significantly enhanced.
However usually this link exists but is not available publicly and managed separately from the Bitcoin network example when you use a off or on ramp for fiat and have to go through AML and KYC processes.
For full anonymity the transaction history stored publicly and in a unencrypted form cannot exist.
Therefore anonymity in Bitcoin is not possible due to how the system works.
There have been attempts at anonymity in the form of coin mixing services and modification of the bitcoin protocol. However these are illegal and have real world consequences.