When you send Monero to someone you only need one piece of information, and that is their Monero address. A raw Monero address is a set of 95 characters starting with a 4. The Monero donation address, for instance, is 46BeWrHpwXmHDpDEUmZBWZfoQpdc6HaERCNmx1pEYL2rAcuwufPN9rXHHtyUA4QVy66qeFQkn6sfK8aHYjA3jk3o1Bv16em.
Because those addresses are long and complex you will often encounter an OpenAlias address instead. For example, Monero donations can be sent to firstname.lastname@example.org or donate.getmonero.org