The purple round port at the top is a DIN connector for an AT keyboard.
It's a little hard to see, but the black round port below the purple one is probably a PS/2 connector, which you can connect a PS/2 mouse or keyboard. Since it's probably expecting an AT keyboard in the top connector, it probably expect only a mouse here.
PC's at this time used PS/2 connectors and not USB, as you can see there are no USB ports on this computer. If you don't have any mouse/keyboard with a PS/2 connector, there are USB-to-PS/2 adapters you can use on a standard USB mouse and keyboard.
The blue vertical port to the left should be a VGA adapter for a VGA cable to an analog monitor.
Now we get to the expansion card slots below.
The first one at the top looks like either for a modem or ethernet.
It's a little hard to tell from just a picture, because both have the same shape port but an ethernet port is larger. Comparing the size of the 2 ports in 2nd slot from the bottom which look smaller, this one looks bigger and is probably for an ethernet network cable.
The next slot below looks like a sound card.
The Gold interface is for a joystick game port.
Green port: audio line out
Pink port: microphone line in
Blue port: audio line in
The next slot below looks like it could be your modem because the 2 ports is the same shape but smaller than the first single port above. One port would be for the phone line in and the other one for a phone line out.
Then the last slot at the bottom.
The red long interface is a parallel port. That's what you use to connect your printer to before USB. I don't know if they even make printers anymore with a parallel connector.
The uncolored smaller port next to the red parallel port is a serial port. I don't think they make any devices using a serial port in like YEARS! But very old devices might connect to a serial port.