Are you referring to the title at the top of the browser? Or the one that starts each post/page just above the content?
If it’s the one at the top of the browser, hat is controlled by the functions called when you have wp_head(); in the header.php file, I’m pretty sure that all Themes offered in the WP repository must have this as a requirement, and all WP-supplied Themes (the ones that come with WP versions) all have it.
If it’s the second one, that’s usually found in the Loop, and depending on your Theme that could be anywhere, but most often is in the content part called in the single.php or page.php template (which either contain the whole loop, or calls a ‘content{}.php’ file where you’ll find the Loop. Once the query is setup, you call the_title(); where you want the post or page title to show, then the_content(); or the_excerpt(); depending on what you want.
SO, what Theme are you using?