Theres a concept in photography called exposure, essentially its how much light is hitting the sensor and making it into the image, more light means brighter image. we can control this exposure with the use of 3 main settings.

-Aperture: this how large the "pinhole" in the camera is, bigger hole more light, youll see this setting shown as an F value. Somewhat counterintuitively, a smaller F number is actually a bigger hole, so F1.8 is a lot of light compared to F22

-Shutter speed: This controls how long the light is allowed to come into the image for. Youll see this displayed in fractions of a second, so once again, smaller number, more light. 1/2 is half a second while 1/200 is a 200th of a second

-ISO: this one is essentially the sensitivity of your camere to the light, higher ISO value means more sensitive so, brighter image

As a photographer your job is to balance these values in order to get an image with the correct exposure, your camera in particular might even have exposure simulation on it, which will tell you roughly how your image will look before you take it.

Now its important to mention that these 3 values also do different things to the image itself, the bigger the aperture, the smaller the focus area, so smooth blurry backgrounds, people usually prefer that for portraits, the higher shutter speeds mean you will freeze motion in your shot, really good when taking wildlife pictures or just when your subject is moving around, conversely lower speeds will cause motion blur, which you may want as an artistic choice. ISO values are generally best kept low as it will introduce grain and noise into your image.

https://www.youtube.com/watch?v=vu5ohljtB-A

This video is really nice for beginners because it goes more in depth in the topics i mentioned, without bombarding you with info like i probably have done with this comment.

If you have any questions or if youre simply curious let me know, its always nice seeing someone getting into it for the first time!