Will i get charged using cellular data/3G?

I was on my iphone and i didn't realize the cellular data and 3G tab was on since i had Wi-Fi on so i didn't see the 3G sign on the upper left side of the screen but rather i just saw the Wi-Fi logo as usual

also just an additional question, only if you want to answer, what is cellular data anyways? As well as 3G, 4G, and LTE? I don't seem to know how it differs from one another

thank you.

Added (1). i only realized this when i turned off the Wi-Fi, but then i just saw the E sign on the upper left instead of 3G

If you're connected to a Wi-Fi connection then it will use your Wi-Fi and not cellular data.

The only difference you need to know about cellular data is speed, from slowest to fastest it goes LTE, 3G and then 4G. Cellular data allows you to have an Internet connection without being connected to Wi-Fi, this is so you can have Internet where a Wi-Fi connection isn't available such as on the road.

Yes, carriers charge for use of data connections (1G-4G)

Cellular data is basically internet access through your carrier. The difference between 3G & 4G is speed. LTE is 4G (though some carriers in the past (& maybe still now) marketed having 4G but that was actually HSPA basically 3.5G.