bit depth

The number of colours between the brightest and darkest parts of an image, ideally saturated white and jet black.   Because this term has derived from computing, and number in computers are binary, this number is always a multiple of two and is the binary power of the number, i.e. 64 colours is a bit depth of 6, 256 colours is a bit depth of 8 (used in JPEG), ordinary camera sensors have a bit depth of 12 (but may not be linear).

In monochrome a single number is used for the brightness (luminosity) range, in the RGB colour space a triplet of three numbers is used; one for the red component, one for the blue component and one for the green component.  If these numbers range from 0 to 255, then it is an 8 bit colour depth in either case (B/W or colour), although in the colour case it is also known as 24 bit colour.

You can read more about this in the first topic which is about as deep as you need to go.  If you do want more, then start with the wikipedia article, but this goes deeper than we need to here.

blur, motion blur.

There are two sorts of blur, the first is caused by lack of, or insufficient, focus and the second is caused by movement of the subject during the exposure.  In reality lenses do not focus at a point (which has no size) but at a small spot called the circle of least confusion.  When this is so small that it is perceived by human vision as a point, then that part of the image is considered to be in focus.  The range of the image where the circle of confusion is small enough to be considered negligible, defines the depth of field.  A favourite term of judges is "pin sharp", but it is all relative; with enough magnification even the sharpest needle looks blunt.

The two commonest sorts of motion blur are linear, which occurs in the direction of travel, and circular on wheel spokes and aeroplane propellers.  An skill in photography is choosing your exposure so that most of the subject is sharp but some motion blur is present to indicate the movement.  Blur can be added in some cases in post production as a correction using the blur tool.

BMP (Bit MaP)

The simplest form of file structure for an image which is just an array of pixel values.   Some bit maps use compression but most do not.  As each pixel is represented by a single number (B/W) or an RGB triplet (colour) they are easy to program and fast in use, and so are popular in operating systems.  There are several different image file types, q.v.

Bokeh.

This is the name given to out of focus highlights in the background.  These are mainly caused by the iris, but can be due to other aspects of lens design and construction.  As they are basically an image of the iris they will often be circular or hexagonal.  Sometimes the effect is pleasing to the eye and adds to the image, sometimes they are distracting and detract from the image.  These are then known as good and bad bokeh.  As with most subjects there is usually more to it which you can follow up on at wikipedia.

Bridge Camera

A halfway point between a compact (small with fixed lens, i.e. not interchangeable though it may have zoom) and a DSLR.  They look like a DSLR, but also have a fixed (non-interchangeable) lens, though often with a 20x (or similar) zoom range.  They usually have the full functionality of a DSLR but are just missing the interchangeable lenses.  Their big advantage is low weight and simplicity.  They are ideal for holidays; everything in one camera pouch instead of a ruck-sack full of equipment.  You could limit yourself to a DSLR with a kit lens for holidays, but it would still be heavier than a bridge camera.  DSLRs have greater range of f/stops; compacts and bridge cameras are usually limited to a few (say f/3.5 to f/8).

burn (see also dodge)

A term originally derived from dark-room days.  To burn part of an image is to make it darker by increasing the exposure of a small area.  Dodge is the opposite process, to lighten part of an image by decreasing the exposure to it.  You now find tools for these functions in photographic software.  For more see the wikipedia article.