The sign / Symbol @, is generally read aloud as “at.” It is also known as the at symbol, commercial at, or address sign. When the File Transfer Protocol (FTP) specifications were being written in July 1972. Someone suggested including some email programs written by Ray Tomlinson, an engineer at Bolt Beranek and Newman, the chief contractor on ARPANET (Advanced Research Projects Agency Network), the precursor to the Internet. U+0040 is the Unicode for the at @ sign.
The at @ Sign / Symbol is frequently used in email addresses and social media to tag specific persons in posts.
Whatever the origins of the @ (at) symbol, the history of its use is more well-known: it has long been used as an abbreviation of arroba in Catalan, Spanish, and Portuguese.

Although it was not on the keyboard of the first commercially successful typewriters, it appeared on at least one model in 1889 and the very popular Underwood models from the “Underwood No. 5” in 1900 forward. The @ sign was first used in email addresses in the 1970s and is now standard on most computer keyboards.
How Can You Use at Sign @ in Day to Day Life
Email Addresses
Technically you can’t find an email address that doesn’t use (at) @ sign.
For example – whenhowandwhat@gmail.com.
Organizations frequently disguise their members’ email addresses or workers on web pages by removing the @ symbol. This well-known approach makes email addresses less accessible to spam algorithms that search the Internet for them.

English Language
In modern English, the @ sign is a commercial symbol that means at and at the rate of. Or at the price of. This has been used occasionally in financial ledgers.
In the Spanish Language
The term amigos have traditionally been used to refer to male buddies and a mixed group or to those whose genders are unknown. Gender-inclusive language advocates would replace it with amig@s in these two examples. In Spanish language they use amigos only when the group referred to is all-male and amigas only when the group is all female.
Malay Language
@ is an informal acronym for the Malay word “atau,” which means “or” in English.
In Madagascar Language
The @ symbol in Malagasy (Madagascar’s official language) is an informal abbreviation for the prepositional form amin’ny.
As Usernames
In social media, particularly on Twitter and Facebook, the @ sign is widely used to signal a reply; for example, @peter to answer Jane’s previous comment. Similarly, @ is sometimes used for “attention” in email messages that were initially sent to someone else.
Twitter usernames are in the form @Anne; this type of username is frequently referred to as a Twitter “handle.”

Computer languages
The @ symbol is used in many programming languages and computer languages, including HTML, JAVA, C#, Python, PHP, Livecode, Forth, and Ruby.