What is the difference between pension investing and regular investing?

The investments can be similar; the difference is in tax treatment and access.

With pension investing your contribution is deductible within your jaarruimte and your capital sits outside box 3 during accrual. In return the money is locked until your retirement date. With regular investing you can always access it, but you miss the tax advantage and your capital counts in box 3. See pension investing and goal-based investing.