Blocktime top left should always be 10 min. so that you have a predictable inflation and the network stays the same speed. Next Diff in the top right-hand corner tells you when the difficulty of finding a block is adjusted so that the block time remains at around 10 minutes. If more miners come online, the hashrate increases, i.e. the power with which blocks are searched for, and the blocks are found more quickly. The difficulty is adjusted every fortnight. If, on the other hand, miners leave, the difficulty has to be reduced. The big number in the middle is the current block in the chain. The one (bottom left) was found 2 minutes ago. 1 Tx (red) is a transaction that had an average size of 299 bytes in the last block (bottom right).

Please evereyone correct me if I'm wrong :)