A frequent pattern in Japanese is the closely related transitive and intransitive verb pair. These will use the same kanji, and usually the same reading for the kanji, but slightly different okurigana. It’s easy to confuse the one for the other if you study randomly, but by studying pairs together, you can learn two verbs in no more time than it takes to learn one.
Let’s look at a couple examples. How about:
Here, 集まる is the intransitive form and 集める is the transitive. Both have the meaning of gathering or collecting. So you might say, for example, ”虫集まる” – “The insects gather” – or ”彼は虫を集める” – “He collects insects”. You can see the only difference is the next-to-last syllable, which moves from the あ row for intransitive to the え row for transitive. Several of these pairs work the same way; another such is 決まる（きまる）- to be decided – and 決める（きめる）- to decide something. But there are lots of different ways in which the pairs can vary and that is just one of the more common forms.
Koichi from Tofugu has put together a good basic list of such pairs on smart.fm, and that’s a great way to get started. This interesting linguistic phenomenon can either really confuse you or make your learning more efficient, so you might as well use it to advantage!
btw I think this is my first attempt at a helpful post directly dealing with Japanese, so if any of you that actually know what you’re talking about (unlike me) have some corrections or additions, I’d love to hear them 😛