1) What is a mirrorless camera?
A mirrorless camera is a digital interchangeable lens camera. Unlike a DLSR, a mirrorless camera lacks a swinging mirror and optical viewfinder. Instead, the light passing through the lens hits the sensor directly, transmits the preview image to an electronic viewfinder (EVF) or the main LCD screen. This allows for mirrorless cameras to be significantly smaller and lighter than DLSRs, among other things.
2) What does ISO mean?
Photographically, ISO stands for the level of sensitivity the camera’s sensor has to light. The higher the ISO number, the more sensitive the sensor and the brighter the image. ISO is an adjustable setting and reaches much higher than it ever did. However, very high ISO settings can sometimes cause grain or “noise” in the image.
When a camera is said to be “very good in low light” it means that there is little to no noise in the higher ISO values.
3) What is a megapixel?
A camera’s sensor is comprised of millions of individual pixels (for “picture element”). Each pixel works individually to capture a tiny amount of light and color, which then gets combined to form the final image. One million of these pixels equals one megapixel. The number of megapixels determines the resolution of the image, and in turn how large the image can be printed or how much it can be cropped. The more megapixels, the larger your prints can be. See this chart for more details.