Laser is an acronym for light amplification via the stimulated emission of radiation. More colloquially, it is a light that produces an intense beam of light. 
A maser is a laser that uses microwaves and it was invented before the laser
Charles Townes and Arthur Schawlow theorized about the laser before building the first maser. The first laser was built by Theodore Maiman in 1960 at Hughes Research Labs, beating out several competing teams, including Charles Townes' team at Columbia University.

Light That Shines Straight

Radiant light spreads from a central emitter. Therefore, the challenge of emitting light in one direction triggered interest in itself. Furthermore, the transmission of energy suffers from deterioration. Finding a way to transmit energy other than through waves whose amplitudes diminished with distance was of great interest.

Curiosity

The laser was invented mostly out of curiosity. As maser inventor Townes wrote in his autobiographical exposition on its invention, he was teased by colleagues for having come up with a nice idea looking for a problem.
In "How the Laser Happened" he wrote: "The truth is, none of us who worked on the first lasers imagined how many uses there might eventually be. This illustrates a vital point that cannot be over stressed. Many of today's practical technologies result from basic science done years to decades before. The people involved, motivated mainly by curiosity, often have little idea as to where their research will lead. Our ability to forecast the practical payoffs from fundamental exploration of the nature of things (and, similarly, to know which of today's research avenues are technological dead ends) is poor. This springs from a central truth: new ideas discovered in the process of research are really new."

Predicted Uses

While not all the uses were anticipated, some certainly were. Gordon Gould, a graduate student at Columbia, had several conversations with Townes about lasers before 1960. In Gould's 1959 conference paper, "The LASER, Light Amplification by Stimulated Emission of Radiation," he noted possible applications such as spectrometry, interferometry, radar and nuclear fusion.

Motivation for the Maser

During World War II, Townes was developing radar for aircraft at Bell Labs. The dispersive nature of electromagnetic waves inhibited the accuracy of radar. Shorter wavelengths meant greater radar accuracy. After the war, Townes continued with radar research at Bell Labs, trying different wavelengths. Townes helped to reduce the wavelength to 1.25 centimeter before transferring to Columbia in 1948.
At Columbia's physics department, Townes used funding from the Navy, which wanted a still smaller wavelength to pursue microwave research. Because of the dispersive qualities of electromagnetic radiation, amplification methods were of a great interest. When the idea of a single-direction microwave amplifier came up in 1951, Townes and Jim Gordon worked on it for three years before creating a working maser.

Skeptics

Applications of the research were not clear to everyone. Nobel Prize winner I.I. Rabi tried to kill the maser project before it was created, not from a belief that it couldn't be made, but instead out of a belief that it was impractical and that resources should be diverted elsewhere.
Many prominent physicists thought it could not even work, based on their knowledge of physical principles. In quantum mechanics, the uncertainty principle developed by Einstein, says that the energy (and therefore the frequency, by E=hv) of a photon can't be known to great precision in a short time. In masers, photons last for a very short time. Therefore, no less than Neils Bohr and John von Neumann thought it couldn't work, even after it had been created. The solution to this apparent paradox is that, though the photons all have the same frequency and direction, which atoms do the emitting and when remains unknown. The emitting atoms maintain an anonymity that avoids uncertainty violation.