Fertilizer is a good idea, but if you are starting out and your main concern is simply keeping your plant alive, you don’t need to get worked up about it. Fertilizer can transform your houseplant from weedy to wonderful, but too much will cause your plant to overdose and die.
Simply put, fertilizer is a product you can add to the soil to top up nutrients that will be naturally replenished in the wild by decomposing stuff. If you decide to fertilize, most plants prefer a boost in warmer months when the plant is growing, however it is a good idea to google your plant’s prime fertilizing times to confirm this.
Dilute fertilizer with water and administer in small doses. It is comparable to vitamin supplements. Plants are good at producing their own food but most will need a boost from time to time. If your plant has been living in the same soil for a long time, another way to restore your plant’s nutrients is by repotting it with a batch of fresh soil. Check the compost packet and information how long its nutrients will last. Most plants live happily in multi-purpose soil except for cacti and succulents which benefit from cacti and succulents composts.