After reading your comment below your question: a field is a function of space-time, no matter its spin: roughly speaking, a field with spin 0
- has scalar values, because its spin is 0
- depends on space and time variables, because it's a field
while a spin 1 field
- has vector values, because its spin is 1
- depends on space and time variables, because it's a field
So the Higgs field doesn't have any Lorentz index ($H$), while the $W$ field has a Lorentz index ($W^\mu$).
A term like $W^\mu W_\mu H$ is an acceptable interaction term because it's a Lorentz scalar (no Lorentz index left). It describes any interaction between a Higgs and two $W$, for example, two $W$ interacting to produce a Higgs.
Edit:
A vector field is a function of space and time that takes vector values.
- In classical physics, they're traditionally written $\vec{F}(x,y,z,t)$, the arrow meaning that the field has vector values in $\mathbb{R}^3$ or $\mathbb{C}^3$.
- In (non quantum) relativity, they're traditionally written $F^\mu(x,y,z,t)$. It's exactly the same thing, except that the vector values are in $\mathbb{R}^4$ or $\mathbb{C}^4$.
It's a bit more complicated than that in quantum field theory because the fields don't have numerical values, but this idea is the same (they're representations of the Lorentz group in 4 dimensions).