Bearer — Definition

Bearer is an APN setting that limits a data connection to specific network generations, such as LTE or 5G.

Leaving it unspecified, which is the usual choice, lets the phone use whatever network is available. Setting it restricts the APN to only the bearers you pick, which is occasionally useful but more often a way to accidentally block your own connection.

In practice

For nearly every phone and carrier, you leave bearer unspecified and everything works. It lives in the deeper APN fields alongside APN type and protocol, the ones you can almost always ignore. Only touch it if a carrier's own documentation tells you to.