Modern carpet is designed to be stretched 1 to 1.5%. Thus if your home is 16′ wide the carpet should be stretched about 2″. This can not be done accurately with a kicker.
Carpet manufacturers are constantly searching for ways to produce carpet that looks and feels better but is cheaper to produce. One unfortunate effect of this has been that most of the changes in methods and materials result in a carpet that is more difficult to install. Good installers are hard to find.
The kicker is the traditional tool of carpet installers and an experienced installer can do remarkably good work with one. However, modern carpet, especially the difficult to install Berbers, requires use of a power stretcher to provide more exact stretching that can be applied with a kicker. A kicker is just a tool with adjustable prongs on one end to grip the carpet and a padded end to kick (with your knee) against.
A Power Stretcher is really just a very heavy jack made for carpet work. They are cheap to rent and expensive to buy and most installers are too cheap and/or macho to use use them. They adjust from about three feet to 28′ more or less and are designed with a toothed end that digs into the carpet and a padded end that is braced against the wall. They are not hard to use, just be aware they can apply enough stretch to tear apart seams or punch through wallboard if the end is not braced against a stud. They are also very heavy.
Seam iron & seam tape are what is used to make seams. Seam tape is paper with a nylon mesh for strength that has been coated with a hot melt glue. The seam tape is placed glue side up under the carpet and the hot iron sits on the glue. The carpet only touches the top of the iron because the temperatures required to melt the glue will also melt the carpet. There is sufficient skill involved that I would not suggest you try seaming expensive carpet your first time. Practice on a rental house or somewhere else where mistakes don’t make much difference.
An incompetent installer can do a lot of damage. In my opinion, it is worth looking for a mobile home carpet supplier who carries carpet in 14′ or 16′ wide rolls. Your choice will be more limited, but you avoid the need for seams.
Tackless strip is the 4′ length of wood with nails pointed down and sharp brads pointed up and angled toward the wall that is used to hold carpet in place. You should be aware that in most older homes the carpet was installed before the walls and held by staples that were covered by the wall. To install new carpet in this kind of house you have to cut the carpet away as close to the wall as possible and then put down new tackless strip all around.
Try to leave about 1/2″ between the wall and the strip. The space is necessary when stretching the carpet because the cut carpet edge needs to go past the strip in order to engage the brads and hold the stretch. Putting the tackless strip too close to the wall makes this a challenge. It might cause wrinkles along the wall and/or force you to trim it slightly. Trimming the carpet too close to the tack strip might also cause the outer edge of the carpet to tear when you put it on the strips. It is better to place the strips correctly first.