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">44AFFq5kSiGBoZ4NMDwYtN18obc8AemS33DBLWs3H7otXft3XjrpDtQGv7SqSsaBYBb98uNbr2VBBEt7f2wfn3RVGQBEP3A</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>