My website uses dynamic URLs, but I've read in SEO forums that Google will not include these in the index. Are static URLs better than dynamic URLs?
What are dynamic URLs? The are URLs that include a question mark (?) followed by 1 or more parameters and values.
In the past, these types of URLs were treated differently to static URLs, or pages with no parameters in the address. Now things are a little better and they will be indexed and included, up to a point. The general guidance is to pass no more than 2 or 3 parameters in the URL, and try to avoid using long numbers as values. Google may detect a long number as a sessionid, and not index the URL/page.
If you can keep the parameter list short, it will probably be ok.
Whether the parameter list is short or not, you may want to consider using mod rewrite to make what's really a dynamic URL appear to be static. This might also improve the readability of the URL for users.
The practice of rewriting URLs is more commonly known as creating Search Engine Friendly URLs (Sefu). This stems back to the days when dynamic URLs were treated differently, but continues today because it improves the readability of URLs, and also creates an opportunity to include keywords in the URL which might otherwise be impossible.