A HYDROXYL GROUP is -OH.
All their names end in ol, which means ALCOHOL.

Here is an example of an alcohol.
Notice the carbon chain in RED, and that there is a HYDROXYL at carbon number 2.
TWO chlorine atoms are added in as well.

1,1-dichloro-butan-2-ol

Step 1
The road is 4 carbons long.
Now 4 carbons = butan
Notice that the numbering starts closer to where the -OH is, and not from where the chlorines are located.

Step 2
The -OH is at carbon number 2.
Hence we say 2-ol. Remember that -OH is written in the name as ol. (not as oh)

We combine butan and 2-ol.
Hence the road name is butan-2-ol.
Notice it is "butan" and not "but".

Step 3
Now the chlorine atoms are found at carbon 1 and 1

We call it 1,1-dichloro
(di means 2 atoms)

We combine all the words into one big word!

Hence the name is:
1,1-dichloro-butan-2-ol