In Google Docs, you can insert an equation and edit it with the equation editor. You can add symbols like summations, integrals, and greek letters with the equation editor, but it is also possible to add them by typing "\sum" "\hat", "\alpha", etc into the equation.
Does Google provide a list of all of these keywords somewhere? It doesn't follow Latex, or the names of the symbols when you go to Insert>"Insert special characters". A lot of keywords that you would expect to work like "\integral" or "\capitaldelta" do not work.
It's a useful feature, but I can't find anything about it.
I found an interesting one at http://www.notuom.com/google-docs-equation-shortcuts.html
For later reference, a protected copy is also available at https://web.archive.org/web/20180625063351/http://www.notuom.com/google-docs-equation-shortcuts.html
So there are at least all these tags available:
letters: \alpha
\beta
\gamma
\delta
\epsilon
\varepsilon
\zeta
\eta
\theta
\vartheta
\iota
\kappa
\lambda
\mu
\nu
\xi
\pi
\varpi
\rho
\varrho
\sigma
\varsigma
\tau
\upsilon
\phi
\varphi
\chi
\psi
\omega
\Gamma
\Delta
\Theta
\Lambda
\Xi
\Pi
\Sigma
\Upsilon
\Phi
\Psi
\Omega
ops: \times
\div
\cdot
\pm
\mp
\ast
\star
\circ
\bullet
\oplus
\ominus
\oslash
\otimes
\odot
\dagger
\ddagger
\vee
\wedge
\cap
\cup
\aleph
\Re
\Im
\top
\bot
\infty
\partial
\forall
\exists
\neg
\triangle
\diamond
relations: \leq
\geq
\prec
\succ
\preceq
\succeq
\ll
\gg
\equiv
\sim
\simeq
\asymp
\approx
\ne
\subset
\supset
\subseteq
\supseteq
\in
\ni
\notin
maths: \frac
\sqrt
\rootof
\subsuperscript
\subscript or _
\superscript or ^
\overline
\widehat
\bigcapab
\bigcupab
\prodab
\coprodab
\rbracelr
\sbracelr
\bracelr
\abs
\intab
\ointab
\sumab
\limab
arrows: \leftarrow
\rightarrow
\leftrightarrow
\Leftarrow
\Rightarrow
\Leftrightarrow
\uparrow
\downarrow
\updownarrow
\Uparrow
\Downarrow
\Updownarrow
binomial: \choose