There are many types of fold that a geologist could study. These include:

Anticline

Syncline

Plunging Folds

and Non-symmetrical Folds

You should also be aware of how to name folds.

But before going into those, you need to understand some basic geologic map skills.

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Structural Geology

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Faults

Geologic Rock Units

• The list on the right is representative of a geologic map legend
• Rocks on maps are listed in age order
• The rocks on the top of the list are the youngest
• The one's on the bottom are the oldest
• This resembles real-life where rocks are deposited, then the "younger rocks" are deposited later on top of them
• These rock units will be used in the proceeding pictures.

Anticline

• A fold in the rocks resulting in an "A" shape (A for Anticline)
• The top side of the box on the left represents the Earth's surface
• The front of the box shows the type of fold
• The dotted line represents the "fold axis"
• The resulting fold has the oldest rocks in the center
• Then rocks repeat on both side of the center symmetrically
• The width of the units on the surface are equal on both sides of the center unit.

Syncline

• A fold in the rocks resulting in a "U" shape
• The top side of the box on the left represents the Earth's surface
• The front of the box shows the type of fold
• The dotted line represents the "fold axis"
• The resulting fold has the youngest rocks in the center
• Then rocks repeat on both side of the center symmetrically
• The width of the units on the surface are equal on both sides of the center unit

Plunging Folds

Plunging Syncline

Plunging Anticline 

• The direction of plunge is visible along the side of the blocks
• This changes the symmetrical pattern seen along the surface
• The new pattern is giant curves on the earths surface
• The "arrow" pattern points in the direction of plunge in an anticline
• The "arrow" points in the opposite direction in a syncline

Non-Symmetrical Folds

Non-Symmetrical Anticline

• Non-symmetrical folds cause the same rock units to be different widths on either side of the fold axis
• On the surface, Synclines and Anticlines will both have the unequal unit widths in non-symmetrical folds
• On the surface, the side with the thinner outcroppings overlie the steeper portion of the fold

Identifying Folds

When identifying folds there are 3 types of qualifiers that would normally be used for a complete description:

Anticline or Syncline

Symmetrical or Non-symmetrical

Plunging or Non-plunging

(typically you don't say "non-plunging", you would just leave off that term)

Examples:

Plunging Symmetrical Anticline

Non-symmetrical Syncline