Hi Snoo these are great questions!
Your mind wanders because that is what it is used to doing. It is untamed and you have to train it. The Buddhists and Yogi's call that the monkey mind as it behaves like a monkey jumping about (no offence intended)! When practising mindfulness you are training your mind to do something very different and it reacts to that. Your experience is very normal but with practice, patience and acceptance it will get easier. My suggestion is to not get frustrated and don't judge yourself. You will have both challenging and good days. Perhaps you might like to try to count your breath. Count your inhalations and exhalations and set up a rhythm. This will enable you to establish a better connection with your breath and act as a preparation for you to watch your breath with greater ease.
Mindfulness and meditation are co existing concepts, however they are not entirely similar. Mindfulness can be practiced formally and informally. Meditation is an example of a formal mindfulness practice. However you can practice mindfulness without meditation. Informal mindfulness practices include eating with awareness, but there are many more out there and you can think of just about anything you like! Be creative with your mindfuless practice.