Help finding a plug-in for seo

I am looking for a basic meta tag, meta description plug-in. I’ve installed several that I have no idea what half of the options are for. I just want a basic SEO plugin that I can set the overall meta tags and description of the site in one place. I don’t need to add individual tags for each post or page. I would edit the header.php page, but if I change themes, then this has to be changed everytime. A plugin would be more ideal.

Can someone point in the right direction to find what I’m looking for?

Thanks in advance!