If you don't want it to automatically detect a card's presence and offer to import images, go to Edit, Preferences and on the General page, untick the "Show import dialog when memory card is detected" check-box.
As Ecosse mentioned, it's very convenient to let LR do the copy from the card into your current folder system and import into its catalog all in one operation. I shoot Nikon NEF in-camera. My working folders are on my C drive, arranged in a folder tree by shooting date. The working files are converted to DNG on import. Meanwhile, the untouched camera-original NEFs are backed up without conversion to an external drive in a folder tree organized by import date. LR does all four operations - copying from card to working folders, converting copied files to DNG, importing DNGs into LR catalog database, and backing up original NEFs to external drive - all in one pass.