Voting mana is the new term for Voting Power. It operates the same way, recharges at the same rate and is nothing more than a name change that came with HF20.

 RC = Resource Credit. RC is an estimation of cost, which includes:  

- CPU (mega)cycles



- State memory



- History size

It is a feature implemented in HF20 to replace the old bandwidth system.

Every action taken on the blockchain has a "cost" associated with it to perform. The larger, the more complex the action, the more space it requires on the blockchain, etc, the larger the cost. In the past that was monitored by the bandwidth number.

 As each of us performed actions our available bandwidth decreased.However it was determined that bandwidth was not an accurate measure of the cost of these operations and also was not scaleable in the future.  A new solution was devised.... enter Resource Credits.

This is supposed to be a more true and accurate calculation  of what resources are needed to perform each action. The longer your post/comment, the more pictures included, etc the more storage it takes on the blockchain, the higher the "cost" to the user.It recharges over a 5 day so you will always go from 0% RC to 100% if you do nothing for 5 days. Personally I just won't use more then 20% or so a day and that way I won't have to worry about running out.

When HF20 was first implemented there were MANY issues with resource credits. There was a bug where initially any action you had taken at all since you first started here was counted against your RC and so most people had a HUGE negative debt and were unable to post, comment, upvote, or even power up since they had no RC to do those actions.

Patches have been implemented over the last few days to correct most of the issues found during the initial launch. There was a patch the other night that increased the available resource pool for each block by a factor of 10. This had the impact of allowing most users to regain most of their RC right away as now suddenly supply outweighed demand and costs of operations were essentially lowered.

Another stated reason for the implementation of RC was to combat the number of spam bots out there. These bots were using an unfairly high amount of resources on the old system and not being charged directly for it. Under RC each account must have enough resource credits to pay for its own actions.

It is hopeful that this will reduce (not eliminate) the amount  of spam comment bots plaguing the system.RC is also a learning system that will attempt to find a balance. This means costs of operations will continually be changing. 

This allows flexibility and scalability moving forward when such features as communities and SMT's (Smart Media Tokens) are implemented in the future.So overall RC was a necessary and needed upgrade to Steem for future growth and scalability but I do not think in any way its implementation can be considered smooth or uneventful.