If you need to record on location or capture environmental samples, then a fully portable, battery-powered field recorder is a more-than solid sidekick. Field recorders can record to SD or microSD cards either via built-in microphones, plugged in microphones or both.
Digital Recorders for Sound Designers
Field recorders are an essential bit of kit for sound designers and sound effect producers. The simplest field recorders can fit in your back pocket and usually feature two integrated microphones to support stereo recording. They're also pretty easy to use. More extensive recorders also have XLR inputs for hooking up your preferred microphones, and most models will be able to record in higher resolutions. Some will have a maximum sample rate of 192kHz, and with a 32 bit floating point bit depth, you're set up with a virtually limitless dynamic range that's able to handle everything from a snuffling bunny rabbit to a raging storm.
Recording Voice Memos with an MP3 Voice Recorder
Dedicated voice recorders are much better for recording voice memos than field recorders since the built-in microphone of any voice recorder has been specifically optimised for speech. As such, the frequency range has been limited so that as little of the ambient noise in the room or space you're speaking in is picked up while other frequencies are strengthened to improve the clarity of your speech. Voice recorders usually have some handy perks like voice-to-text functions and an automatic pause function that halts recording whenever silence is detected.
Recording Software: iOS & Android Apps
Almost everyone has a smartphone these days, and these pocket-sized widgets grant access to countless recording apps - essentially putting a recorder in the palm of your hand. The built-in microphone of the average phone isn't really set up for making professional recordings though, so you can pick up an Android or iOS compatible microphone that will immediately improve the sound quality. You can get iOS or Android microphones designed for an array of uses. For example, you can get stereo condenser microphones for recording gigs and concerts or clip-on microphones for video reports, vlogs, and interviews.
A Microphone or Line Input for Your Camera
Field recorders are also essential tools for film makers. Not all cameras have XLR inputs and the built-in microphone is usually just intended to give you an audio reference in post-production. Luckily, there are audio recorders designed for integration into a video production setup. They'll usually come fitted with a 1/4 inch mounting point so they can be screwed directly onto the body of a DSLR or DSLM camera. These recorder also have a mix-output that can be connected to the audio input of your camera so you can use it as your audio reference that will help sync the sound and video up later.