Your core is a series of muscles in your midsection. Not to be confused with the abdominals.
Think of your core as a foundation to a building. Weak foundation leads to a weak structure. We use our core every day so it would make sense that you train it quite often also.
Strengthening your core will lead to such benefits as:
Decreased risk of injury to lower back
The plank is one of the most effective exercises to build a strong and stable core and I’d advise incorporating some form of plank into your training regime 2-3 times per week. Here are four different variations to get you started.