The following is the Wikipedia definition for Skills Based Routing:
“Skills based routing (SBR) is a call assignment
 strategy used in call centers to assign incoming calls to the most 
suitable agent, rather than simply choosing the next available agent. It
 is an enhancement to the Automatic Call Distributor systems (and IVR 
systems) found in most call centers. The need for skills based routing 
has arisen as call centers have become larger and dealt with a wider 
variety of call types.”
 
Best way to describe Skill Based Routing is with an example.  If you 
have 3 agents in a call group each having a different skill level in 
their certain field :
But each person may know a bit about the other skills. Each Agent has a weight rating:
| Agent | 
Windows | 
Linux | 
MacOSX | 
French | 
English | 
|---|---|---|---|---|---|
| Agent 1 | 
100 | 
50 | 
25 | 
100 | 
0 | 
| Agent 2 | 
25 | 
100 | 
50 | 
100 | 
100 | 
| Agent 3 | 
50 | 
25 | 
100 | 
100 | 
50 | 
Example:
4 calls come, 2 asking for Windows support, one for Mac Support and one for Linux support
Agent 1 was free gets the first windows call
Agent 2 was free gets the second windows call
Agent 3 was free get the first Mac call
Caller 4 waits until an agent gets free for the system to reevaluate the skill table
Advantages of this method over a traditional Queue (ACD ):
 
If you want to use Skill Based Routing, the minimal requirements are:
 
You can create multiple Skills on the ScopTEL PBX using the Telephony -> Queues and Agents (ACD) -> Skill Based Routing menu.
A Skill Rules set is a list of conditions that can be created on Telephony -> Queues and Agents (ACD) -> Skill Based Routing menu. Each
 conditions are evaluated against each Agent in order to see if it 
matches. The call is distributed according to the matching rule.
Each rule has two parts:
You can get more details about Conditions, Rules,  and Arithmetic/logical operators, that can be used on a rules, on the Definition tab.
 Important Note : Never use <= or >= operators otherwise the rule will be omitted !
Once the Skill Routing Rule is created the list view will look like the following :
 
 
Now that all the skills are created you may assign them to the agents on the  Telephony -> Queues and Agents (ACD) -> Agents menu under the Options tab.   You can specify  custom skills on a per agent basis like :
 
If you have multiple agents that share same Skills, you can go on  Telephony -> Queues and Agents (ACD) -> Skill Based Routing and create Skill Groups that can be assigned to agents.
Now that skill rules are created and skills assigned to agents, you must assign the Skill Based Rule  to a Queue (ACD). In this sample, we assign the rule to a Queue directly on an Auto Attendant (IVR):
Note:  You must  issue a Commit in Telephony GUI after configuration modification.
Be carefull to have at least one Agent skills matching the 
first Rule of the Rules Set, otherwise the Queue Application will hangup
 incoming calls, omitting the following rules.