Communication over radio seems easy enough until there is a lot of information that needs to be relayed. Chaotic comms can lead to misunderstandings and as a result poorer efficiency on the battlefield. For that reason a few ground rules of radio communication help to keep it clear.

The most important rule is to only say the important thing and to do it smoothly, quickly and in a way that everyone can understand you (clearly). It helps to take some time before sending a message to organize what you want to say in your mind. 
To avoid talking over each other it is important to mark when our message is over and what kind of response or lack thereof we expect.

So when our message is over but we expect an answer from the receiver we end our message with over.

When our message is over but we don’t expect or don’t need a response, we simply end the message with out.

Additionally, if we want the receiver to give us some time to respond we simply respond to their question with standby.

If we have to stop the transmission but our message isn’t over, we simply end the transmission with brake. And then continue after a short period of time. This call can also be used to clearly change the receiver of the communication. Additionally if we have something very important to say and want to make sure the radio chatter stops, we simply start our message with brake, brake, brake and everyone knows to stop talking and listen to the message.

The radio discipline described is obviously for the purpose of mil-sim gaming whereas IRL it might sound similar, it is often way more structured.

Examples of radio communication:

Alpha to HQ, over
Alpha this is HQ, transmit, over
HQ, Alpha requests medical supplies to grid coordinates 1 8 5 brake 0 5 6 numpad 3, how copy over
Alpha, HQ, good copy, medical supplies to grid coordinates 1 8 5 brake 0 5 6 numpad 3, over
Alpha confirms, over
Alpha, in 5 mikes supplies will be delivered by helo, mark LZ with green smoke, over
Alpha copies, supplies in 5 mikes, marking LZ with yellow smoke, Alpha out

In this example Alpha asked HQ to organize a supply run for them. They gave their location, HQ confirmed it to make sure they heard right and told Alpha to mark an LZ which Alpha also confirmed.

Anvil actual to Anvil 1-1, come in 1-1
Actual this is 1-1, over
1-1 we’ve got reports of movement around the buildings 100 meters west of your position, break…
…
move to the north-west to overwatch that area, how copy
Actual, 1-1, good copy, moving north-west to overwatch the buildings west, over
Brake, brake, brake, Anvil 1-5 to all anvils, contact, bearing 120, distance 500 meters, two T-72s in the open moving left to right, Anvil 1-5 engaging, out
This is Anvil Actual, good copy 1-5, brake, all anvils reposition to engage targets, bearing 120, distance 500 meters, out
Anvil 1-3, two times T-72 destroyed, bearing 130, 1-5 confirm targets destroyed
This is 1-5, affirm, targets destroyed, good shooting 1-3, out

The acting commander of the unit with codename Anvil was telling one of the sub-units to check out a contact report, but before the communications could be finished, Anvil 1-5 noticed two targets that could threaten friendly forces. Realizing that was the priority target, they stopped other comms and reported the contact using the 3D method. 1-3 was able to destroy the T-72s and double checked with 1-5 to make sure it was the same target and 1-5 responded with a pat on the back.