Everything worth knowing, nothing that isn't.
How it differs from a group
In a broadcast, each recipient gets a private, individual message — they do not see the other recipients or each other's replies, unlike a group chat. It is the audience container for one-to-many sends. See /answers/what-is-bulk-messaging.
Keep it consented and clean
Every number on the list should have opted in; validate numbers, suppress opt-outs, and segment for relevance. A stale or unconsented list wrecks deliverability. See /answers/sms-opt-in-best-practices and /products/hlr-lookup.
Segment rather than blast
Broadcasting the same message to one giant list underperforms sending targeted messages to smaller, relevant segments. See /answers/sms-marketing-best-practices and /answers/what-is-a-sms-blast.