When using acronyms and terms that might not be familiar with your audience they should be explained. Yesterday I once again fell quilty to throwing up terms that might not be so familiar especially with people outside of the tech industry.
Tech is the biggest industry sector nowadays, the only industry where the biggest companies are worth trillions. The biggest ones are often referred by a few different acronyms or terms.
The first one is the Big Five, sometimes also just Big tech referring (currently) to Alphabet, Amazon, Apple, Meta and Microsoft. Before, there was FANG (Facebook, Amazon, Netflix, Google), which soon after was extended by another A (adding Apple) to make it FAANG. At the time (2013) those were the biggest, most influential tech companies that were said to dominate their respective markets.
These terms are usually also strictly about US based companies (even though it wouldn't be a case that they so happen to be the biggest one sin the world). China is the number 2 tech hub having it's own Big Four called BATX including Baidu, Alibaba, Tencent and Xiaomi.
Despite their huge market capitalization there has been quite drastic changes in the top. Good example being Netflix that was included in the original FANG-gang but has since fallen far behind the other giants. Same is happening with Meta in recent years and (debatable tech) companies like Tesla are raising up (even though also falling back recently in valuation).