Binary is the base 2 number system. We typically use the decimal (base 10) number system to count, but any base actually works.
Decimal:

6234 means that we have:	6 [1000s]	2 [100s]	3 [10s]	4 [1s]
Another way to see these is as powers of 10:	6 [103s]	2 [102s]	3 [101s]	4 [100s]

Binary works the exact same way, except the base of our numbers is 2.
Binary:

0110 means that we have:	0 [8s]	1 [4s]	1 [2s]	0 [1s]
Or as powers of 2:	0 [23s]	1 [22s]	1 [21s]	0 [20s]

This gives us a total of 6 in base 10. So we say 0110₂ = 6₁₀.

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You can click on the bits here to turn them on or off to see the result, or add/subtract 1 at a time.

0	0	0	0	0	0	0	0
–							+
000000002			=		00010
0 + 0 + 0 + 0 + 0 + 0 + 0 + 0			=		0 + 0 + 0