What is PCIe? Understanding PCIe Slots, Cards and Lanes

Is it okay to put Gen 3 SSD in my motherboards Gen 4 pcie slots? pcie 3 0 in 4 0 slot To be specific, a PCIe slot has an 8 GTs transfer rate per lane, while a PCIe slot has a 16 GTs transfer rate per lane Moreover, the pcieslot O problema são as placas da AMD RX6500XT e RX6400 que são PCI-e e operam em modo X4, qdo vc coloca elas em um slot PCI-e a mesma vai

pcie 2 slot 1 PCI express x16 slot, integrated in cpu, supporting PCIe x16 mode 1 PCI express x16 slot, integrated in chipset, supporting PCIe x2 mode 1 PCI