How do boron 10 and boron 11 differ?

For starters they are both isotopes of Boron. The boron in the periodic table has an atomic weight of 10.8, which is basically the average of all of boron's isotopes' atomic weights.
An isotope is an atom of an element with the same number of protons, but a different number of neutrons.

This means that the atomic number (proton number: in boron's case this is 5) is the same (which is good, as it's the number of protons which determines what element is which), but the mass number will be different.

For example. Carbon 12 has 6 protons, 6 neutrons and 6 electrons. A well known isotope of Carbon 12 is Carbon 14. Note that the number is always the mass number. This means that in Carbon 14, there are still 6 protons and 6 electrons (we know this as it is still carbon; hence still has 6 protons, and is still neutral; hence still has 6 electrons), but there are 8 neutrons.

So the difference between boron 10 and boron 11 is that boron 10 has one less neutron than boron 11, or, equally, boron 11 has one more neutron than boron 10.

This means that they will have the same chemical properties (will react the same), but will have different physical properties (eg. Boron 11 will be slightly heavier than boron 10).