I'd recommend crash course on youtube if you are just starting a concept and want a basic and fun overview of it. Their videos are informative, but aren't boring. They also have videos for many other subjects, which you can check out too! Specifically for biology, I definitely recommend checking out the amoeba sisters. They're funny and make very entertaining videos that I enjoy watching in my free time, and cover topics explicitly in the VCE biology course. In a similar line, I definitely recommend Douchy's biology podcasts by Andrew Douch, which if you search on google will come up. If you're bored on the bus or train to school (doesn't apply now) or even in the car, you can listen to his podcasts, which are tailored to the current VCE biology study design. He spends ample time on many different topics, and many students find him a huge help for biology 3/4. Lastly, the good old-fashioned Khan academy. Yes, the videos may sometimes go deeper than what you need to know, but we are here to learn, not blindly memorise facts just to reproduce on a SAC or exam (I mean, you can do this, but it's more fun to immerse yourself in the content!). Whenever I don't really understand a concept, and this isn't restricted to biology, I turn to Khan academy to see if they can help (which they usually can) or I'll just do a quick google search to read a few articles until I understand the concept. Often, going in-depth is necessary if you really want to understand the nuances of a topic that you simply cannot learn if you only adhere to the study design. It's really good to gain this knowledge, even though it isn't necessary to know, because it'll help understand the why or how behind the particular topic you are learning.
Hope this helped!