Marxist = A follower of Karl Marx, the inventor of Communism. Here's a simplistic explanation of communist thought. In capitalism, the wealth produced by the whole population isn't equally shared by all participants. All profit comes from inputs + means of productions. Example when you make sell a hamburger:
Means of production: cooking equipment, shop (lease or own).
Inputs: meat, bread etc., human work (burger flipping guy).

If you pay all this $3 and you sell the burger $5, the $2 of profit are only possible because you underpay the burger flipper, who doesn't own the cooking equipment or (part of) the physical shop. So you are "stealing" from the workers, who should collectively own the shop and share the $2. Ownership of the burger enterprise (the shop, pans, cooking equipment, meat and bread orders etc.) should be distributed among the workers.

In practice, collective ownership turns into a nightmare where the big political bosses own everything and the burger flipping plebs own nothing. No one is motivated to open burger shops. The economy stagnates, poverty spreads.

Some people get richer than others because they own the means of production (factories) and pay the workers less than fairly.

(Bitcoin) Maxi = There's bitcoin and there are shitcoins. The latter are very different from bitcoin. Bitcoin is good, shitcoins are bad.
Examples:  JJG and many others here.

I hope this helps.