Is the wifi connection speed thro router the same as wired ethernet

Hi, I presume that my wifi access point ssid, from my router is given to me thro, bb connection .
Further that , i get now my wifi connection, thro , wireless nano adapter , the ethernet port not working.
My query:
I am having a bb speed of nearly 10 mbps download and .50kbps upload. never mind the upload.
Yesterday , i tried the speed test at ookla and my speed was reduced to 5mbps thro the wifi connection.This is probably because, smart phones were used along with the pc at that time.
I have disabled wifi on all other devices , except my pc and the speed test shows the original speed that I got it from using ethernet.
Is my presumption correct that,
the speed given by the bband connection thro ethernet /wifi are the same. I mean, the access point , ssid is thro wifi/ethernet the same?
and if you use some more devices , that this speed is getting distributed to number of devices accessing wifi

Hi, Samuria, thanks for the reply. I usually get a fixed 12mbps download speed thro, my bb connection. Now that the Ethernet lan port is damaged, I have been using a wifi dongle to access my wifi to my pc.
My question is, is the speed thro Ethernet and wifi differs, in the sense, that wifi mode is different from wired Ethernet mode.Does it provide the speed thro, wifi and ethernet and speed is shared among the devices?
If suppose, I use only the pc, the speed would be 10 to 12 mb and if I use more than 3 devices, this speed is divided among the devices?
So be it wired or wireless , what your plan, the speed is distributed among the devices?