Creating SVGs with popular image editing packages and services
While SVGs can be opened, edited, and written in a text editor, there are plenty of applications offering a Graphical User Interface (GUI) that make authoring complex SVG graphics easier. Perhaps the most obvious choice is Adobe’s Illustrator (PC/Mac). However, it is expensive for casual users, so my own preference is either Bohemian Coding’s Sketch (Mac only: https://www.sketch.com/), which still isn’t cheap at $99 a year, or Figma, which is cross-platform and also uses a subscription-based model that is currently free for the starter plan. Check out Figma at https://www.figma.com/.
If you use Windows/Linux and/or are looking for cheap options, consider the free and open source Inkscape (https://inkscape.org/en/). It’s by no means the prettiest tool to work with, but it is very capable (if you want any proof, view the Inkscape gallery: https://inkscape.org/en/community/gallery/).
Finally...