Updated today (2nd December, 2020) this Search Engine Optimisation plugin from the Dutch company managed by Joost de Valk is probably the most favoured SEO plugin with All in One SEO running it a close second.
Yoast says it will improve your WordPress SEO, you will write better content and have a fully optimized WordPress site using this plugin.
It has a simple dashboard at the foot of each post or page and operates a simple traffice light system to achieve improvements.