There are various types of tuners that may be built into a television:
NTSC (National Television System Committee) is the analog television broadcasting standard used widely in North America. It is referred to as a 525-line standard, but actually displays only 480 lines. NTSC is to be replaced with new DTV (Digital TV) standards in the coming years.
The PAL (Phase Alternating Line) standard was introduced in the early 1960's and was implemented widely in Europe. It has a wider channel bandwidth than NTSC as it runs on 635 lines.
ATSC (Advanced Television Standards Committee) creates the technical standards for the US digital television system (DTV). These standards are expected to be used in most new televisions, as the US television system shifts from analog to digital.
QAM (Quadrature Amplitude Modulation) tuner is present in some new digital televisions and similar devices. It enables direct reception of digital cable channels without the use of a set-top box. QAM tuners can be likened to the cable equivalent of an ATSC tuner which is required to receive over-the-air (OTA) digital channels broadcast by local television stations.