Increasing stitches simply means that you need to add an extra stitch or stitches to your knitting.
By adding stitches you will be shaping your knitting and making the fabric wider. For instance when you knit a sleeve for a sweater your upper arm is wider than your lower arm and wrist area so you will gradually start increasing stitches as you knit up the sleeve.
There are many ways to add extra stitches but for now I will show you the basic knit increase called knit front and back (KFB), also called the bar increase. If you look at your knitting after the increase you'll notice a little bar. Don't worry though. It is hardly noticeable.
By knitting increases this way you will be making two stitches out of one and it's really easy to do.
The first part is just the knit stitch but let's go through it again.
With your right needle push through the first stitch on your left needle from front to back. Then take your working yarn (ball end) and wrap it around right needle.
Then bring it through the stitch on the left needle just like the picture on left. (Right photo)The new knit stitch is now on the right needle. And this is where it changes a bit in order to work the increase. Don't drop the loop off the left needle.
With your right needle go into back of stitch on left needle. Then wrap yarn around right needle (just like the knit stitch) counterclockwise.
With yarn wrapped around right needle lift left needle up and over wrapped yarn on right needle. And there you go. Pretty great isn't it? Now you know the knit front and back kfb increase.
Increasing stitches on a purl row? You can do that?
It is a little trickier to work but it can be done.
You see most knitting increases are worked on the right side (knit side) which means that you would make a knit increase.
Sometimes though you may get a knitting pattern that asks you to increase purlwise. It doesn't happen too often but at least this way you'll know how to do it.
You may have to manipulate your needles but you'll get it.
Basically what you will be doing is the purl stitch but you won't drop the loop off your left needle. Rather, you will work a purl stitch in the back of the same loop. It's just like the knit front and back only this is the purl front and back.
Here's how to do it.. Get your fingers ready.
The beginning starts off with the purl stitch so make sure your yarn is in the front of your work. With your right needle insert it into the first loop on the left needle just like purling.
Bring yarn around right needle counterclockwise, snug it up a bit.
With right needle and the yarn still wrapped, bring it through loop on left needle. Up to this point you have just done a purl stitch. Let's keep going here...
Do not drop the loop (stitch) from your left needle. You will now work into the back of that loop to create a purlwise increase.
This is the tricky part and I tried very hard to make the picture as clear as possible so that you can understand. Make sure your working yarn is still in the front of your work.
In this picture I moved my left needle around because you have to insert the right needle in the stitch on the left needle from the outside. See how I am doing it in the picture? I know this is tricky but you can do it.
See how in this photo on the left the stitch is twisted? Don't worry its supposed to be like that.
Bring working yarn around right needle counterclockwise.
Bring your right needle with the yarn wrapped around it through back of stitch on left needle. See how my right needle is going through the stitch kind of backwards on the left needle? Just keep bringing the needle through.
There you go. You can now drop the loop from the left needle.
There it is. The right needle has your new purl increase stitch
Increasing stitches isn't so difficult is it? Now you know how to do basic knitting increases and purl increases.
Your knitting pattern says to increase stitches evenly across a row. What do they mean exactly?
A lot of times in sweater patterns for instance, after you have worked the ribbing, you will often see that you have to increase more stitches for the body of the sweater. And the increases are usually done at evenly spaced intervals across the row.
Here is a great explanation for helping you figure out the proper way to increase stitches evenly across a row. It also explains how to decrease stitches evenly as well.