An acronym is a short name formed by combining the first letters of the complete name. UCLA, NYU, and UNM refer to universities, and IBM, AT&T, and GM refer to companies. We sometimes sign our initials instead of our complete signature, and we are familiar with messages such as RSVP, BYOB, and TGIF. This basic idea can be used to devise a mnemonic for things you want to remember.
A common example is the acronym "HOMES" to help you remember the names of the Great Lakes. Of course, you have to know the names for the mnemonic to help, but if you know them, their first letters spell HOMES. This is a good place to remind you that the mnemonic may only give a hint of the answer (in this case, just the first letter), and the mnemonic offers no understanding. Information such as where the Great Lakes are located, how they were formed, and what cities lie on their banks is not included in the mnemonic. You already have to know what you're trying to remember for a mnemonic to help.
Acronyms do not have to be perfect. Suppose we adopt the rule that vowels do not count, and we need to remember to get milk, bread, potatoes, and tomatoes at the store. The first letters are MBPT. If you can think up a word (or phrase) that contains those four letters, adding only vowels, you can remember one thing instead of four. When order is not important, you can rearrange the letters in any way. My first mnemonics are "bump-it," and "be empty." I like the second one because I can make the sentence, "I don't want to 'be empty' when I return home," as an easy-to-remember mnemonic for the occasion.