For most hardy indoor plants, normal tap water is perfectly fine, as long as it’s not extremely hard or treated with very strong chemicals. Many people use tap water for years without any issues. However, some sensitive plants – especially certain tropicals or carnivorous varieties – can sulk if the water has too many salts or chlorine.
If your water has a noticeable chlorine smell, you can fill a bucket and let it sit overnight; a lot of the chlorine will evaporate by morning. Using that “rested” water is gentler on plants. Hard water can leave white marks on soil and pots over time – that’s mineral build-up, not instant poison, but it can accumulate.
If you notice leaves getting brown tips regularly despite correct watering habits, water quality might be a factor. In that case, you can switch some plants to filtered or rainwater and see if they respond better.
For most beginners, though, tap water plus reasonable care is enough. Don’t overcomplicate it until your plants give you a reason to.