About Mysql and gd library loading

For Mysql and gd library loading problems, what is the connection between mysql and php we have installed ,, there is also why we can use the gd library without installing the gd library but only need to open the gd Library, and, why does one need to be installed without installation? what is the difference ;; I can't figure it out. mysql is a database system, and it can work. net, jav about Mysql and gd library loading
What is the connection between the mysql and php we have installed, and why can we use the gd library without installing the gd library ,,,, why do I need to install one without installation? what is the difference? I cannot solve it;

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Mysql is a database system that can be connected to other programming languages such as. Net and java. it communicates with the outside world through the socket communication protocol.
In the php installation package, GD library extensions and mysql database extensions (such as mysql, mysqli, and pdo_mysql) are provided, but are not enabled by default.
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Mysql is a database. If php does not open the mysql support extension, it is not supported. Therefore, you may need to clarify the expansion and database mysql. Gd is also an extension. These extensions are already in the php release package by default, so we generally only need to enable the support.