Are JPGs and PNGs vector?
The short answer, No.
Although you can have high resolution files, image files are compressed and flattened file types. When you make these files wider and taller than the size they were made at, they become pixelated, blurry, and often text becomes illegible.
Image resolution is determined by how far from a printed piece or digital billboard you are. Always ask for specifications when providing files to ensure your design and marketing will look its best.
A good rule of thumb is that you can always make an image smaller but resist the urge to stretch an image or make it larger than the size it was created. You are losing detail and the result might be visibly pixelated.