What's the difference between bolt-on and set neck guitars?

Two completely different philosophies for attaching a neck to a body, and the choice affects everything from tone to repairability to how much a neck adjustment will cost you down the line.

Bolt-on

Exactly what it sounds like — the neck is attached with bolts (or screws) into a pocket routed into the body, no glue involved. This is the Fender approach, and it's also how most Taylor acoustics attach their necks (with their signature shim-adjustable NT neck joint). Bolt-on construction is generally cheaper to manufacture, and critically, it's much easier to service — a neck angle problem on a bolt-on guitar can often be solved with a shim in an hour, rather than the multi-hour, higher-risk process of steaming apart a glued joint.

Set neck

The neck is glued into the body, typically using a dovetail or mortise-and-tenon style joint, and it's meant to be a permanent, one-time connection. This is the traditional approach for most higher-end acoustics (Martin, Gibson, Guild) and a lot of higher-end electrics (Gibson Les Pauls, for instance). Set necks are often associated with slightly better sustain and resonance transfer, since there's a continuous glued wood joint rather than a mechanical bolted interface — though how much this actually matters tonally is genuinely debated among builders and players.

What it means for repairs

This is the part that actually affects your wallet. A bolt-on neck angle issue is a same-day, lower-cost fix. A set neck angle issue is a full neck reset — steaming the joint apart, reshaping, and regluing — which is a bigger job, a bigger bill, and carries more risk to the finish and the instrument overall.

Which is "better"?

Neither, categorically. They're different tools solving the same problem with different tradeoffs between tone, cost, and long-term serviceability. Knowing which one you have tells you a lot about what a future repair might actually look like.