QoS or Quality of Service, is a type of application. This application controls how your router will forward data though your router. Normally, this occurs on a simple First-In First-Out rule, that is data that comes in first, goes out first. By adding QoS to your router, you will change the way this works. This increases performance of router for specific applications, lowering latency and typically shows improved network performance for applications that need it.
QoS in MikroTik is a bit different than other QoS systems. Other systems typically have a check box for VoIP QoS, however, RouterOS is not the same. RouterOS you create and build your OWN QoS System from scratch. If you want to prioritize Terminal Services or Remote desktop services, you can, however, you can also prioritize pings as well. Depending on your VoIP platform, you can identify the data to and from your platform and then provide QoS services.
On top of the standard QoS services, that is, packet reordering. MikroTik also support MIR and CIR. With that said, you can build a QoS system that allocates bandwidth for your VoIP or other latency sensitive systems, and slow down other types of traffic to make room for your priority traffic.
Link Technologies, Inc, will assist in creating a QoS system specifically for your business needs, not what other people think you need. Forget about pre-packaged systems, as you will need something that fits your network, not theirs. Typical QoS systems can take around 1 - 2 hours to create, once its done its yours!