A:Answer Hi! I'm just a beginner, so I'm not super knowledgeable, but I'll try to help you out!
So first off, the biggest difference is gonna be the zoom range. The 18-55mm has a significantly shorter zoom range than the 70-300mm. The 18-55mm can take basic pictures at semi-close range, such as portraits, while the 70-300mm is for long-range pictures such as a mountain in the distance. This is the most imporant difference between the two.
Also to be noted is the difference in f-stop sizes, which denotes the range in apertures. This controls your depth of field. In the case of the 18-55mm, you have an f-stop of between 3.5-5.6, while the 70-300 has an f-stop of 4.5-6.3. Essentially what this means is the 18-55mm lens will do a better job of isolating a foreground object while leaving the background to be more blurry, a common trick used by portrait and still life photographers, and the 70-300mm lens will do a better job of keeping the entire photo in focus, as is common with landscape pictures.
Sans these basic differences I don't really have enough knowledge or experience to explain the nuanced differences between these two lenses. Hopefully this gives you a good starting point, though!