The period used for buying and registering new players is often termed as the Transfer Window. There are two windows for transferring and registering new players; the summer transfer window, which tends to begin from the 1st of June in case of most European countries, and the winter transfer window, which tends to begin from the 1st of January. The timings vary according to the countries of course.
Owing to the competitiveness and the revenue structure of the European clubs, they overshadow their American, African and Asian counterparts more often than not. Of late we've seen China making big strides in trying to sign players for big money, but eventually, we could see the Asians use money more pragmatically in the coming years.
The highest fee paid for a player is £198m. It was only last summer when Ligue 1 side Paris Saint-Germain paid the astronomical fee for the Brazilian international from Barcelona. The Spanish side then paid £128m for Liverpool attacker Philippe Coutinho who also makes makes the list of top three most expensive players. Coutinho's move to Liverpool was the most recent of the three. Kylian Mbappe, also signed by PSG, is the other player in the top three.