I think Gerd's solution was the most helpful.
In case somebody stumbles across this, a more detailed and complete solution...
The vanilla studio.sh starter-shell script sets an env-variable:
LD_LIBRARY_PATH="$IDE_BIN_HOME:$LD_LIBRARY_PATH"
that it then exports. The IDE_BIN_HOME is set by using the location of the studio.sh file (somewhere in the middle - usually [android-studio]/bin).
When an emulator is launched through Studio->Manger->Tools->Manage AVDs this env-var is prefixed with android-SDK/tools/bin.
Meaning when you start it standalone, you didn't set that env-var.
Gerd's solution adds the lib to the system lib-search-path.
Another approach would be to create a wrapper that takes care of this so that it's only set when needed and (possibly) other things are also set.
#!/bin/bash
export JAVA_HOME="/usr/lib/jvm/java-BLAH"
export STUDIO_JDK="$JAVA_HOME" #This is also used in studio.sh
export IDE_BIN_HOME="/home/you/android-studio/bin"
export Anroid_SDK="/home/you/android-sdk"
export LD_LIBRARY_PATH="$Anroid_SDK/tools/lib:$IDE_BIN_HOME:$LD_LIBRARY_PATH"
cd "$Anroid_SDK/tools"
./emulator64-x86 -avd AVD-NAME-1 -gpu on &
./emulator64-arm -avd AVD-NAME-2
This is probably a bit overdone, but it's complete ;)
Depending on Distro/Setup JAVA_HOME may be preset, so you could drop that line. If you constantly use the emulator, you could also add something like
export LD_LIBRARY_PATH="[YOUR Studio PATH]/tools/lib:$LD_LIBRARY_PATH"
to your .bashrc or .profile file.
But to answer the actual question: It means that the emulator wasn't able to run (hardware-accel?) OpenGLES, and that it's using software routines to implement/emulate OpenGLES :D
To enable emulator to find the desired lib, make sure you have proper (3D-Accel.?) graphic-card drivers installed, then choose one of the above (wrapper shell or (bash-)session-init settings).
Note that newer versions of Android-Studio have forked out the SDK