Let see an example of a user-agent string
Mozilla/5.0 (Linux; Android 7.1.1; TONE-m17) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/76.0.3809.89 Mobile Safari/537.36
This is a typical user-agent string whose content is combined of 4 parts
* Mozilla/5.0 (Linux; Android