No.
Mindfulness is a practice that aims at bringing attention outside of the mind and into the senses, ‘lightening’ the cognitive load. It is a good entry point into the Buddhist tradition, it does the double duty of giving you quick wins that build your confidence for later, more intense meditative practice, as well as moderating your expectations for what is going to happen while you are practicing. Too many people sit down to meditate, and feel like they’re getting nowhere because their aims aren’t in line with their level of practice. You can certainly reach the first jhana (what Buddhists call an identifiable ‘level’ of concentration) with mindfulness practice.
The bare minimum of mindfulness practice is to bring attention to the senses, gently bring it back when it wanders, and to cast judgment out of mind as it arises. As you get better, judgment arises less, and attention wanders less. You can add basic meditative techniques to it, such as box or triangle breathing, and if you just add whatever it will slowly morph into general, undirected, trance practice.
This includes stuff like chakra opening. Basically, without a map, it’s hard to tell where you’re going. If you want a more directed practice, then this is where you need to start boning up on Buddhist literature. This will invariably expose you to Sanskrit terminology.
You might be surprised to know that there is no Sanskrit word for mindfulness as the West knows it. This is because it is a Western practice which is only loosely based on Buddhist technique. What it is very good at is lowering the activity of the “default mode network,” an area of the brain that lights up whenever you’re not directly focused on anything else. Mindfulness directs your mind into a state of constant focus, keeping things like fears and worries and anxieties from running rampant over your conscious mind.
This issue, anxiety sapping conscious will, well, isn’t something that is half as prevalent in the East as it is in the West. In fact, if this is something you’re hoping to solve with mindfulness practice, then bothering with the third eye chakra or Sanskrit is just going to get in the way. If you’re just looking to be a little less scattered, then sure, anything to focus the mind is fine, go wild. But if you’re an anxious sort, then reading about a bunch of strange new things that are fuzzily-defined to the Western mind can just as easily cloud you with more anxiety over whether you’re doing it right, even though at its very basic level, mindfulness is extraordinarily simple and easy, about as simple and easy as it is to make a ‘meditative’ practice that’s not just ‘take three good deep breaths’.