Vitamins A, C and E get talked about together because they all act as antioxidants, but they do it in different parts of your body. C is water soluble so it works in the watery parts of your cells and bloodstream. E is fat soluble so it works in cell membranes and fatty tissues. A is fat soluble too, but it's mainly a vision and immune nutrient that also has antioxidant activity as a bonus.
The reason they're better together is regeneration. Once Vitamin E has neutralised a free radical, it's been used up and becomes oxidised itself. Vitamin C can pass back its electron and regenerate the E, ready to be used again. It's a tag team rather than three soloists.
For Vitamin A, we use Retinol rather than beta carotene. Beta carotene needs to be converted to retinol in your body, and some people convert poorly. Retinol skips that step and gives you the active form directly.
For C, ascorbic acid is the form your body absorbs and uses most efficiently. The clever marketing forms (liposomal, buffered, esterified) cost more and don't deliver meaningfully better results at the doses found in a multivitamin.