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 <spanclass="long-term">46BeWrHpwXmHDpDEUmZBWZfoQpdc6HaERCNmx1pEYL2rAcuwufPN9rXHHtyUA4QVy66qeFQkn6sfK8aHYjA3jk3o1Bv16em</span>.
Because those addresses are long and complex you will often encounter an @OpenAlias address instead. For example, Monero donations can be sent to <spanclass="long-term">donate@getmonero.org</span> or <spanclass="long-term">donate.getmonero.org</span>