Hello M M
The MAC and IP addresses are used together to allow network devices to communicate with each other. IP addresses allow the communication from end to end while MAC addresses are used within a specific subnet.
Think about it this way. If I was to give you my postal address, and I told you the number of my house on my street is 176, that would not give you enough information for you to find me. If you had already reached my street, then yes, you could find me with just that information.
The same is true of the MAC address. If I gave you the MAC address of my web server, you would not be able to reach it from your computer. But if I gave you my IP address, you would reach my network, and then using the MAC address (learned via ARP), you could communicate with the specific device on my network.
Remember that network communication functions in layers. The Network Layer is responsible for routing from end to end of a communication, and uses the IP protocol, while the Data link layer, where MAC addresses are used, is responsible for getting a frame to the appropriate device within a network segment.
It is indeed difficult to get your head around it especially if it is the first time you are going over these topics. It will take time, but I suggest you go over the following lessons which will help you understand more fully:
Also, take a look at the CCNA course linked below, and focus on Unit 2: Network fundamentals, which includes all of this information.
I hope this has been helpful!