Creatine is probably the most researched ergogenic used in sports
nutrition.

Based on multiple studies, we see that it is one of the few
supplements that genuinely proves effective for muscle building. 1,2
There are several mechanisms through which it aids the more efficient
conversion of energy in the mitochondria. Creatine helps the transport
of energy for your muscles, significantly enhancing the effective utilisation of carbohydrates. 3
In terms of muscle building, it prevents protein breakdown and protein
oxidation by creating an environment that is ideal from inhibiting
protein breakdown and protein synthesis. This prevents muscle loss and activates muscle building. 4 Ideally creatine works better with
consistently training. But it also prevents muscle loss to a certain
extend without training. Hence, it ought to be taken on rest days as
well as days in days that your train.
Moving on, disclaimer this is not discouragement for supplementing
with creatine. As it depends on your goals, if your goal is primarily to
build muscle, by all means use creatine. But if your goal is to lose fat
consider not taking creatine as it does prevent fat lose during the
exercise and potentially after as well, as its role is to use carbohydrates
effectively, this, hinders your body’s utilisation of fat as fuel. It’s
worth noting that you can still build muscle through resistance training
without the use of creatine.
While no supplement can surpass the benefits of consistent training
and mindful dietary choices.

1 https://journals.physiology.org/doi/full/10.1152/japplphysiol.01170.2001?rfr_dat=cr_pub+
+0pubmed&url_ver=Z39.88-2003&rfr_id=ori%3Arid%3Acrossref.org

2 https://pubmed.ncbi.nlm.nih.gov/10449017/

3 Photo by Aleksander Saks on Unsplash

4 https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6921011/