If you've got a laminate floor and surrounding baseboard, and there's a small gap where the trim meets the floor, it means either the floor wasn't even and straight, or the trim contracted after it was installed. Either way, it's an easy fix. Latex caulk will seal off that gap and will expand and contract with the movement of the materials afterward. You can buy it in just about any color, so matching the floor is usually pretty simple.
Vacuum along the gap with a vacuum hose to pull out any dust or debris that's in there. Dampen your sponge with rubbing alcohol. Wipe it all along the seam between the baseboard and the floor, to get it completely clean. Let it dry.
Insert the caulk tub into the caulk gun. Use a razor knife to cut off the tip of the tube at a 45-degree angle, making the hole about 1/4 inch wide.
Jam a 3-inch nail down into the hole to break the seal inside. Dampen the rag with water and wring it.
Compress the trigger of the caulk gun until it rises from the tube and starts to come out the end. Stop the flow of caulk by pressing the release latch at the back of the gun. Wipe off any caulk that came out, using your rag.
Press the tip of the gun to the joint, at one end of the wall, with the 45-degree angle of the cut flush over the space. Compress the trigger until the caulk flows out. Pull the gun slowly backward as you continue to compress it, laying the caulk in a line. Don't stop moving the caulk gun or compressing the trigger, but keep it consistent until you've covered the whole span in a thin, even bead.
Lift the gun from the joint. Press the release latch to stop the flow.
Wet your thumb on the rag and run it all along the caulk line, pressing and smoothing the caulk flat into the joint. Stop as needed to wipe the excess caulk off your thumb with the rag. Get the caulk the way you want it, and then let it dry for 24 hours.