The meaning of different parts in the naming of glucose

There are two main types of glucose, $\alpha$-D-(+)-glucose and $\beta$-D-(+)-glucose. 
Can anyone please explain what is $\alpha$,D or (+)?  

![Glucose](https://i.stack.imgur.com/TJei5m.jpg)  

So (maybe by permutation and combination), how many types of glucose are there?




Glucose can exist in the open form or cyclic form. 


![enter image description here](https://i.stack.imgur.com/60rKo.png)


In the open form, there are only two types, D-glucose (illustrated in Fischer projection above) and L-glucose which is the mirror image of the above. 


Experimentally, D-glucose rotates plane polarize light clockwise, hence the symbol "+", and L-glucose rotates plane polarize light counterclockwise, hence the minus symbol. For more information on the meaning of + versus - see: <http://en.wikipedia.org/wiki/Dextrorotation_and_levorotation>


In the cyclic form, there is an additional chiral center, so there is alpha (where 3 OH groups are on the same side of the ring) vs beta (where 2 OH groups are on each side of the ring) as ilustrated in the drawing of the question. 


Each of alpha and beta have a D and an L form, so there are 4 types in the cyclic form. 


So in summary, there are only two types in the open form, but 4 types in the cyclic form. 


 3