BGP (Border Gateway Protocol) is the routing protocol that connects autonomous systems: each network announces “here are my IP prefixes, here is how to reach me”. The entire Internet runs on it.
For a business, use case number one is multi-homing: with your AS and your addresses, you announce the same prefixes to two transit providers; if one fails, traffic fails over to the other within seconds, without changing a single address. Path preference is steered with local-pref, AS-path prepend and MED.
Without your own AS, a pragmatic alternative exists: take addresses from a carrier present at both your sites — the same AS announces the pool at both locations and your IPs follow to the backup site. That is exactly what our co-presence search verifies.