There are a few properties of differential forms that you didn't mention.
First and foremost an important quality they enjoy is being anti-symmetric.
Anti-symmetry of course cannot be seen when only dealing with one forms, you have to look at two forms and up.
What is anti-symmetry?
Well consider the function
Now if I exchange x and y I will pick up a negative sign for my function.
In the case of two variables, there are only two rearrangements of the input, namely doing nothing and exchanging x with y.
This concept is rooted in Abstract Algebra and is related to the Symmetric Group.
The symmetric group is a collection of mappings from
Or all possible rearrangements of n letters.
I don't want to get very much into group theory here but this is what's going on.
Differential forms interact with members of the Symmetric Group denoted:
By satisfying the following relation:
$$\forall \sigma \in S_n, \quad \omega \in \Lambda^k(M)\\
Where m is the number of transpositions in the permutation. Also called the signature or sign.
The key here is that differential k-forms are a special kind of tensor. The kind of tensor that interacts with $S_n$ in the manner described.
What else can I say about them..
-Well they allow us to define the determinant of a linear map for one. I'm not going to run through the construction unless you want me to but it is certainly worth looking at.
-They give rigorous meaning to the cross product in three dimensions and higher.
-They provide the tools for defining div, grad and curl. Which are the result of applying a special map called the exterior derivative to a zero form, 1 form and 2 form.
Again worth looking at.
-I think most importantly they provide a theory of integration and of course Stoke's Theorem. When you study generalized Stokes you will see that the Fundamental Theorem of Calculus, Green's Theorem, Divergence Theorem and classical Stoke's Theorem are all the same but deal with different flavors of forms.
Let me know if you have any further questions, I left most details out.
An excellent reference is 'A Geometric Guide to Differential Forms' by David Bachman.
In answer to your question:
The situation is as follows. You have a curve in say $R^3$ and you parameterize the curve. Now at each point along the curve you have a Tangent Space. What is a Tangent Space? It's a vector space attached to the curve where all the tangent vectors live. In your mind picture it as nothing more than the tangent line.
In our case the vector space is one dimensional. But in differential geometry, when we study surfaces, the dimension of the surface is characterized exactly as the dimension of its tangent space.
Now you have a one-form defined along this curve. When we integrate the one form the idea of partitioning the domain as we do for Riemann Integration is the same. We partition the curve and as we do in each partition interval we choose a tangent space and have the one form act on a vector in that space. Then you add them up to get your number.
So the long winded answer is when you get down to it, integrating a form and evaluating a form are two different things. You build the integral of a form by evaluation and summing. So I think in essence the two cases are different but of course I could be wrong. Maybe someone else could elaborate more on this.
I can help with wedge product too if you want.
Unfortunately or fortunately, however you want to look at it. Tensors are algebraic objects and to really understand them you need some algebra which of course takes some time.
Hope this helps.