It takes a while to earn enough HIVE to post or comment. If you buy some HIVE you can send it to your HIVE wallet an then Power Up the HIVE (Think of this as a savings account with a lockup period) once powered up it gives you more abilities on the HIVE blockchain. The more HIVE you have powered up the more impact you have (Votes carry more weight and allow everyone you interact with to earn more) The idea of hive is to create a network of people that you can interact with regularly and assuming you provide valuable content the more interactions your content gets with high level HIVE'rs everyone makes some money by promoting the best content(or at least most popular) Its great because it takes the power away from centralized biased algorithms and makes the content curated in a much more democratic manor.