RouterBOARD is a router in a form of embedded PC board. It comes with different number of ports (miniPCI, miniPCIe, ethernet, SFP). Some models have integrated 802.11 wifi cards.
RouterOS is the linux based operating system. It runs both on RouterBOARD devices and x86 compatible devices like PCs.
RouterOS supports multi-core and multi-cpu systems, and it can be installed on various storage units: HDDs, SSDs, CF cards, USB and many other
RouterOS supports many network interfaces, including the latest 10 Gigabit ethernet cards, 802.11a/b/g/n/ac wireless cards and 3G modems.
There are six types of Mikrotik Licenses (Level 0 (Trial), 1 (Demo), 3 (CPE), 4, 5, 6). More details on the licenses can be found here
The Dude network monitor is application by MikroTik which simplifys overview and management of your network. It can automatically find all devices within specified subnets, make network layouts, monitor your devices and respond to alerts.