Secure string generator is a tool which generates cryptographically secure pseudo-random bytes (binary data) which are afterwards converted into hexadecimal representation. Nowadays this approach is considered much more secure, mainly because random generated bytes couldn't be easily predicted comparing with classical random string generators. Therefore this is the best tool for cryptography, for example used for when generating salts, keys or tokens.
As the base parameter you can specify string length. Recommended minimum length of 32 characters is also set as a default value. In more options section you are able to set how many secure strings should be generated in number of strings field (default set to 1).
If you would like to generate more customized string, where you can define character set, try to use random string generator which is displayed in related tools below.