Number bonds are pairs of numbers that add up to a target number. Number bonds to 10 can be described in different ways. You can say '6 and 4 make 10', or '3 and 7 more equal 10', or even that 'double ...
These are decimal numbers, and dots above some of the digits make them recurring decimals. One dot means the digit under it repeats infinitely. In other words, it goes on forever (and ever and ever).