hi,
if i am working for example on one Mikrotik sxt (360 degrees) that is connected to 3 mikrotiks sxt. i have read that when working with Mikrotik point to multi point, we have to set the 1st one as ap bridge mode, and the other 3 as station mode,
why? and what is the difference between the ap-bridge mode and station mode.
Can you please help me?
Thanks in advance!

what is the difference between the ap-bridge mode and station mode.

Basic operation of WiFi is point to multipoint. The role of central device (access point) are numerous:

• it broadcasts system information, such as SSID, encryption configuration (WEP, WPA, WPA2), etc.
• selects frequency channel to work on. Also selects frequency channel width (20,40,80,160MHz)
• maintains list of connected devices
• in TDMA type of communication AP schedules transmission time slots for other devices (in MT world that's nv2). In usual type (802.11) of operation each wireless device (APs and stations) can start to transmit at any time but need to implement collision detection (similar to mechanism used in half-duplex ethernet networks).
• in a given wireless "mini network" there can only be one AP. If multiple APs operating same SSIDs are in the same area, each of them creates its own "mini network".

device in station mode is quite passive in comparison:

• listens to broadcasts and only and connects to AP with desired SSID
• before entering connected mode it passively scans for SSIDs on all supported frequency channels. After entering connected mode follows AP's frequency selections. Regarding channel width it can negotiate with AP to use subset of supported channel widths (e.g. use only 20MHz channel if AP supports different channel widths including 20MHz).
• doesn't know about other connected devices. If data needs to be transmitted to another station connected to the same AP ... station doesn't care and sends it to AP regardless. It's AP which sends such data to the other station if allowed (ROS has a setting about that)
• in TDMA listens to scheduler channel and only transmits during granted time slots
• in a given wireless "mini network" there can be many stations, but each station can be part of single "mini network" (read: it can only be connected to one AP at the time). This limitation can be bypassed if station uses more than one radio, then it can be connected to multiple APs, as many as number of radios available (if station has 2,4GHz and 5GHz radios, it could simultaneously connect to 2 APs, one in each frequency band ... ant hen use some kind of bonding mechanism to use both in parallel)

"AP bridge" - access point (where clients can connect to)
"Station" - client mode (clients can connect to access points)

what is the difference between the ap-bridge mode and station mode.

Basic operation of WiFi is point to multipoint........

this is what i wanted to know, thanks, much appreciated