There are apps for iPhone that have audio tools to help you learn how to pronounce a particular word you're looking up. For instance, one app has a little speaker icon next to each word's pronunciation respelling. Tap that to hear how the word sounds. But you don't need a third-party app because iOS has a pronunciation tool built right in, and you don't even have to leave the current page you're on.
When you're reading and come across a word that you're not sure how to pronounce, either long-press or double-tap it to select it, depending on which app you're in. For instance, in Notes, you can do either, but in Safari, sometimes you can only long-press. After the word is highlighted, the black contextual menu should appear with options for cutting, copying, pasting, and so on. If not, tap on the highlighted word once to make it show up.
The option we're looking for is "Speak." If you don't see it right away, tap the right arrow to view more options. If you don't see it after doing that, make sure "Speak Selection" is on in Settings –> Accessibility –> Spoken Content, then try again.
The benefit of Apple's built-in "Speak" tool over third-party apps' pronunciation options is that you can select multiple words at once, so if there's a phrase you're having trouble with, select it all, then hit "Speak." Even better, it works on emojis too, so if you ever wanted to know what that poop emoji is really called, highlight it and hit "Speak."
And you're not limited to just your default language — this is also an excellent way to learn what the symbols mean in Japanese or how something spelled in Arabic sounds. Furthermore, you don't even need to use it for pronunciations — you can highlight an entire article and hit "Speak" to have your iPhone read it to you.
If you want to change the "Speaking Rate" (how fast it talks), make it "Highlight Content" (if you're using this to listen to articles), change "Voices" (if you don't like the default digital speaker), and more, you can do so from the "Spoken Content" settings in "Accessibility."